I. Field of the Invention
This invention relates generally to implantable medical devices, and more particularly to a method of precisely defining the moment of death of a patient in whom such a device is implanted.
II. Background of the Invention
Implantable medical devices, such as cardiac pacemakers, pacemaker/defibrillators and other cardiac resynchronizing devices, are frequently used to treat patients suffering from cardiac abnormalities, including arrhythmias, chronotropic incompetence and congestive heart failure. Such patients are often aged or in poor health. By providing properly timed electrical stimulation to the heart, cardiac output can be better linked to metabolic demand, leading to an improved quality of life for the patient.
State-of-the-art cardiac rhythm management devices generally comprise a programmed microprocessor connected in controlling relation to a stimulation pulse generator. At times dictated by a software program executed by the microprocessor, the microprocessor-based controller applies pacing pulses to cardiac tissue via electrodes on electrical pacing leads. The stimulator system will also include one or more sensing circuits for detecting, amplifying and shaping cardiac depolarization signals (electrograms) picked up by the electrodes on the pacing lead. These depolarization signals are applied to the microprocessor-based controller and are used by the software in controlling the times at which stimulating pulses are applied to the heart.
In demand-type pacemakers, pacing is integrated with a patient's own sinus rate and pacing pulses are generated in the absence of an intrinsic heartbeat or in accordance with some other pacing algorithm. Assuming that a pace pulse is of a sufficient amplitude to result in capture of the myocardial tissue, a detectable depolarization signal occurs.
Modern cardiac rhythm management devices include sufficient memory for not only storing programs and programmable parameters used in executing the program, but also to store for later read-out, electrograms covering a predetermined interval of time. By reading out electrogram information using the telemetry capabilities of such devices, a medical professional is able to gain considerable insight into the patient's cardiac performance and the efficacy of a pacing therapy being administered.
When a person dies, it frequently proves helpful to know the exact moment (date and time) when death took place. Also, if a patient in whom a cardiac rhythm management device has been implanted dies, stored electrogram data and other information relating the device's performance may be captured at the time of death, aiding a medical professional in determining how the patient's heart and the cardiac stimulator were functioning up until the moment of death.
It is accordingly a principal purpose of the present invention to provide a method for sensing and recording the time of death of a patient in whom a cardiac rhythm management device has been implanted along with other data.